Flexible shaft power tool



June 24, 195v8 E. F. BURTON FLEXIBLE lSHAFT POWER TOOL FiledA Nov. 2,1953 1N V EN TOR. bu/Ae 52,270#

BY Arroz/wwf- United States Patent O This invention relates to flexibleshaft power tools such as drilling, grinding, and erasing machines andis directed primarily to improving and simplying the control means forthe electrical power drive and making such machines safer and moreconvenient to operate.

Flexible shaft power tools presently available consist generally of anelectric motor mounted on a suitable support, a flexible shaft andcasing means attached to the motor, and a power head carried by theouter, or free, end of the flexible casing means, together with acontrol switch mounted directly on the motor, or remotely located on thefloor for foot operation, with a conductor means extending to the motor.

The rst type is particularly inconvenient for the ilexible shaft isnormally three feet or more in length and it is diflicult if notimpossible to operate the switch while hol-ding the power head inworking position. When working with a cutting or abraiding tool mountedin the power head it is desirable more often than not to locate the toolin position before setting it in motion. This purpose is obviouslydefeated if the switch is too far away to reach with the operators freehand.

The vsecond type is used in professional work where the operator usesthe tool enough to develop the proper coordination between hand and footbut it is not particularly desirable for amateur use because of thenecessity for special coordination. Moreover, foot operated switches aresubject to considerable damage while lying on the floor and must bemoved from place to place as the operator changes his position. Inaddition, the cord leading from the switch to the motor is frequently inthe way and is also subject to damage.

The present invention eliminates all of the objections to the previoustypes and provides a simpler, safer, and more convenient means forcontrolling the motor. It is particularly desirable for amateur usebecause of its natural feel, the operator using the same hand to guidethe tool and to control the application of power thereto.

Essentially the present improvement consists in providing an elongateflexible electrical conductor means which is operatively connected tothe power circuit of the driver motor, the conductor means extendingalong the length of the flexible casing and preferably wrappedtherearound and secured thereto, and mounting an electric switchdirectly on the power head of the tool, with the conductor meansconnected to the switch so that the operator, while holding the powerhead in one hand, may operate the switch with a finger, thus enablinghim to locate the tool exactly in the desired position and then, withoutmoving the tool or his hand, set the tool in operation.

The presently preferred embodiments of the invention are illustrated inthe accompanying drawing, in which:

Figure l is a general elevational view, with a portion broken away, of aflexible shaft power tool embodying the simplest form of the invention;

Figure 2 is a longitudinal sectional view of the power head of the toolshown in Figure l;

Figure3 is a sectional view taken on line 3-3 of Figure l;

Figure 4 is an exploded view in perspective of the adjacent end fittingsof the power head and flexible shaft and casing assembly of a modifiedform of the invention incorporating a built-in wiring system;

Figure 5 is a similar view of the adjacent end fittings of the flexibleshaft and casing assembly and the motor;

Figure 6 is a sectional view taken on line 6-6 of Figure 4;

Figure 7 is a perspective view of a modified power head with portionsbroken away to show a modification of the control switch; and

Figure 8 is a sectional view taken on line 8-8 of Figure 7.

As generally illustrated in Figures l and 2, the power tool includes anelectric motor 10, a flexible shaft 12 and flexible casing 14 connectedthereto, and a power head 16 carried by the outer, or free, end of thecasing. The power circuit within the motor housing is connected to anoutside source of power by conductor 11.

The power head 16 includes an external shell 18, bushings 20 and 21, arotatable shaft 22 carried thereby, and bushing retainer 24 secured tothe shell. The shaft is provided with a bore 26 thruout the majorportion of its length to receive an eraser stick 28 which is held inadjusted position by chuck 30, attached to the open end of the hollowshaft and provided with a chuck ring 32. The rightward end of the shaft,as viewed in Figure 2 is provided with a squared hole 34 to receive thesquared end 36 of the flexible shaft 12 to be driven thereby, and theassembly is held together by collar 38 screwed onto bushing retainer 24,the flange 39 of the collar engaging the flange 40 on the end of theflexible casing 14.

A casing member 42 is mounted on the power head and provides protectionfor the snap acting electric switch 44 located therein. The controlmember 45 extends a slight distance outward of the casing to provideaccess for finger operation. Elongate, flexible electrical conductormeans 46 extend along the length of the flexible casing and areconnected operatively at their inner ends to the power circuit of themotor. They may be connected directly in series with the circuit or maylead to a relay to cause operation of the circuit. At their outer endsthey are connected to the terminals 47 and 48 of the switch 44.

It will now be seen that when the operator is ready to use the device hemay grasp the power head in one hand, place the cutting or abrading toolin operativo position, and then with his fingers depress control member45 with his finger to actuate motor 10. He may do this with easeregardless of the length of shaft and casing assembly 14.

While the conductor means may extend substantially directly parallel tothe casing it has been found desirable, in order to avoid any reductionof the flexibility of the casing, to wrap the conductor means helicallyaround the casing with a pitch of at least one full turn per foot oflength of the casing. ln either form the conductor means may be held inplace by one or more collars or clips 50. Figure 3 shows how theconductor means lies closely adjacent the surface of the casing.

Figures 4 to 8 illustrate a modification of the invention in which thewiring is, in effect, built-in, In Figure 4 the power head end fitting52 carries a driven shaft 54 provided with a bore 55 having a keyway 56.The adjacent end fitting 58 of the flexible casing carries a drivingshaft 60 provided with a boss 61 having a key 62 for engagement with thedriven shaft. Fitting 58 carries electrical plugs 64 to which theconductor means 65 are connected and fitting 52 carries receptacles 66toreceiveplugs v64.- shown, extend from receptacles 66 to the switch onthe ppwer head., Collar 68 screwson to fittingA 52 to hold the ttingsirrassembled relations- 'Pin' 69 on-tting352 engages socket 70 in fitting58 tionandtorelieVe they electrical connections ofshear andiotherrloads;1

In'Figure 5, the fitting 72 carries drivenlshaftf7ffi=ratvk the innerend of the-ilexible/'shaft and casing-assembly. The Yshaftis providedwith-non-circular bore 75; Fitting 7.6 on themotor housing-carriesdriving shaft 77 with a non-circularend portion 78-to engage bore 75.Receptacles 79 inriitting 72 are connected with conducto'rmeans` 65fwhile/plug means-8tl-are^connected Vto a conductor, notshown, whichIextendsinto the motor-housing for operative connection to the powercircuit asV described above withv referenceV to the` modification ofFigures 1 and 2. Pin 81 and socket 82 perform the same functionY asipin691and socket 70 inwFigure 4. The collar- 84 screws onto fitting 76` toholdthefittings in assembledrelation.

Asbestseen` in Figure 6, thel flexible sheath 86 envelops the iiexiblecasi11g87 and the conductor means 65 and holds tbemin assembled relationwhile permitting the necessary flexing which occurs during use of thetool. It alsoV provides protection againstY dirt and abrasion. Thesheath Vmay be mechanically laid-over'the assembly orgtheconductor meansmay be molded-into its asindicated in Figure 6.

To complete theV enclosure of the electrical4 system theswitch mechanismmay be modified as shown in Figures'7 and 8, in Whichra rigidcasing-member 88 surrounds the power head 90, its upperV porting beingenlarged to -receivethe switch 92 which is generally similar, to theswitchi of the-first modification. An opening `941 is provided intheupper, or radially outer, portion ofthe casing member andthe controlmember-96 ofthe switch is located in said opening and substantiallyflush with the contour ofthe casing member so that it may be depressedto close the circuit.

A sheath 98 of elastically deformable material, such as rubber,enclosesthe entire casing member and covers thev opening 9 4 to excludeall foreign matter fromthe switchV mechanism. It thus protects theswitch also from the mechanical damage and prevents inadvertent operatoprevent relative Yrota- Y asaogefa Further conductormeans; not-- tionsSinceu it is elastic, itmayV be` deformed` under` finger pressure sothat the control member may be depressed to actuate the motor.

While the preferred embodiments of the invention have been illustratedin the drawing and described above, it will be apparent to those skilledin the art that various changes and modiiicationsmay be made Withoutdeparting from the spirit yof the invention, and it is intended that allsuch changes'and modifications shall be embraced within the scope ofthe-following claims.

I claim:

1. Controlmeansfor an` electric y-power'tool having a power head,comprising: a rigid casing'v mounted on said power head and providedwith an opening in its Iradially outer side; an electric switch mountedwithin said casing and having a depressible control member extending, in

Y non-operating condition, into said opening and beingsubstantiallyflushwith the-contour of said casing; and an elastically` deformableshield extending over said-openingto exclude foreignmatter and toprevent inadvertent` operation of said-switch, the shieldbeingdeformablel under iin-gerpressure to providevfor depressionofsaid-Acontrol member.

2; Control means as claimed'in claim 1, in which saidshleldY sr anelastically deformable sheath surrounding-y said power headan'dsaidcasing.

References Cited in the tilev of this patent UNITED STATES PATENTS`Great Britain Jan. 8,

